In a letter, Salvini told Prime Minister Giuseppe Conte he could authorise the "alleged" minors to leave the Open Arms ship despite it being "contrary to my policy", AFP reported.

Still, the remaining 105 adults and two accompanied children must stay on board in what the charity Proactiva Open Arms said were "untenable" conditions.

"Evacuation of unaccompanied minors completed," Open Arms tweeted after the Italian coastguard collected the children and took them to Lampedusa port, some after more than two weeks at sea.

The migrants, who have been out at sea for the last two weeks, were picked up off the coast of Libya by a charity rescue ship. At least 134 migrants, mainly from Sub-Saharan Africa, were on board the Open Arms ship before the children were allowed to leave. A spokesperson for the Open Arms aid group, operating the charity ship carrying the migrants, said citizens of Eritrea, Somalia, Nigeria and Cameroon are among those on board.

Thirteen people, who Open Arms said were seriously traumatised or requiring medical attention, were moved off the boat on Thursday.

"They are self-harming and getting angry with other people in the group," Alessandro di Benedetto, a psychologist with Italian aid group Emergency, told RAI radio after examining five of those brought ashore.

"Some of them are having suicidal thoughts, so they think it is better to die here than go back there," he added.

Salvini, who has built his popularity on a vigorous campaign against illegal immigration, has resisted calls to let the ship dock despite six European Union nations agreeing to take the migrants in.

France, Germany, Romania, Portugal, Spain and Luxembourg have said they will help relocate the migrants, but the reaction from Salvini's interior ministry was sceptical.

The controversial Italian politician has questioned whether the migrants on board the Open Arms ship have health concerns.

In Brussels, a European Commission spokeswoman said the EU welcomed the other countries' cooperation and was ready to give operational support once a solution was found for landing the rescued migrants.

Land in sight

Prime Minister Giuseppe Conte, who belongs to no political party but is close to Salvini's 5-Star movement, accused him of exploiting the issue.

This standoff is the latest in a series that has seen charity boats caught up in European political tussles over the past year, drifting at sea as states argue over who is responsible for opening their ports.

"We are living an unbearable agony on board," Open Arms said on Twitter, posting a video of people lying close together on the deck, swaddled in blankets.

"Land in sight and no solution. The rights of 134 people are being violated with every passing minute. If European politicians are incapable of setting limits, what do we have left?"

The issue highlights the breakdown of Italy's ruling coalition and how immigration has become central to Salvini's plan to take his right-wing League party out of government and drag the country to elections in the hope of coming to power as prime minister.

Salvini's tough anti-immigration rhetoric has helped boost his popularity at the expense of coalition partner the 5-Star Movement, but his surprise bid to bring down the government and call an election is running into trouble.

On Friday, he tweeted a picture of himself gazing upwards and the message: "Timidity? Appeals to false notions of compassion? Open ports? Thousands of arrivals? Not in my name! Italy, hold your head up high again!"